Trion formation in two-dimensional Ruddlesden-Popper lead iodide perovskites

Two-dimensional Ruddlesden-Popper (2D RP) perovskites are promising light-emitting materials thanks to their high photoluminescence quantum yields and tunable emission wavelengths.^[1] In low dimension semiconductor structure, the formation of trion, a complex bound state of an exciton and an electron or a hole, is highly possible. For example, trion formation and its dynamics have been observed and extensively studied in 2D transition metal dichalcogenides (TMDs)^[2] and hybrid perovskite quantum dots (PQDs)^[3]. It is reported that trion formation in the material determines its luminescence efficiency and emission energy, and therefore the suppression of trion formation is important for photoluminescence quantum yield enhancement.^[4] Presently, there is a debate on the origin of the lower energy emission peak in 2D perovskites which was assigned to be biexciton, trap state, in gap exciton, magnetic dipole emission, and possibly trion. Here, we present our work on the dynamics of the low energy emission peak in 2D hybrid perovskite, phenyl-ethyl ammonium lead iodide (PEA)₂PbI_4, by time-resolved magneto photoluminescence and electrical doping photoluminescence spectroscopies.